UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8 1595Wynkoop Street DENVER, CO 80202-1129 Phone 800-227-8917 http://www.epa.gov/region08 

## JUN 2 22007 Ref: 8P-AR Mr.**Stev~** Wright ColumbiaFalls Aluminum Company 2000 Aluminum Drive ColumbiaFalls, MT 59912 Re: Results of"Subjectto" Visibility Modeling for Best Available Retrofit Technology (BART) and Request to Conduct a BARTAnalysis for BART-Eligible Units at Columbia Falls Aluminum Company Dear Mr. Wright: OnJune 19, 2006, EPA received a letter from the MontanaDepartment ofEnvironmental Quality that stated it was withdrawing its efforts to meet the requirements ofthe Regional Haze Rule (RHR) specified at 40 CFR 51.308. On September 27,2006, EPA Region 8 sent a letter notifying you that we would be conducting modeling to determine which sources in Montana are "subject to" the Best Available Retrofit Technology (BART) requirements in the RHR as part of our effort to address the requirements ofthat rule. Since it was determined that Columbia Falls Aluminum Company (CFAC) was BARTeligible, we informed you that CFAC would be included in the modeling and asked you to certifythe datathat would be used for this modeling. EPA Region 8, with the assistance ofthe Western Regional Air Partnership (WRAP), has now completed the visibility modeling for determining those Montana sources subject to BART. Based onthe modeling,.EPA Region 8has determinedthat your facility is subject to BART. Accordingly, we are requesting that you submit a BARTAnalysis for CFAC within 90 days of this letter, as explained below. In modeling CFAC's visibility impacts, EPA Region 8 followed the approach for determining ifa source is subject to BART, including the specifics onhow the modeling should be performed, set out in the final RHR and EPA's "Guidelines for Best Available Retrofit Technology Determinations" (BART Guidelines). See 70 FR 39104, July 6,2005. The BART Guidelines can be found at Appendix Y to 40 CFRPart 51. EPA Region 8'svisibility modeling also generally followed the protocol outlined in the document "Draft CalpuffBART Modeling Protocol for Federal Mandatory Class 1Areas" (MontanaDepartment ofEnvironmental Quality, September 2006). Anelectronic copy ofthis protocol is located on EPA Region 8's website at http://www.epa.gov/region8/air/mtregionalhaze.html. Where necessary, we made slight variations to the protocol, such as instances where meteorological data was not available for a certain site.2 States (orEPA) have several options for detennining whethera source is subject to BART, includingthe use ofdispersion modeling to detennine whether an individual source may be reasonably anticipated to cause or contribute to any visibility impainnent in any Class I area. When dispersion modeling is used, part ofthe process ofdetennining whether a source is subject to BART is the selection ofa deciview threshold against which to measure the visibility impact ofa source. Forits analysis ofMontana sources, EPA Region 8 has established a threshold of 0.5 deciviews as the appropriate threshold based on the number and distribution ofsources impacting Class I areas in and around Montana. Ifdispersion modeling predicts that a source will have visibility impacts of0.5 deciviews ormore at a Class I area onthe 98th percentile of values, EPA Region 8 considers that source to be subject to BART. Further infonnation regarding this approach to detennining whether a source is subject to BARTcanbe found in section IILA ofthe BART Guidelines. ForCFAC, the modeling results show a maximum 98th percentile impact within a Class I area of4.54 deciviews, which exceeds the threshold of0.5 deciviews. Since CFAC exceeds the 0.5 deciview threshold, and thus may reasonably be anticipated to cause orcontribute to visibility impainnentin one or more Class I areas, EPA Region 8 has concluded that CFAC is subject to BART. A summary ofthe BART modeling results is enclosed. The enclosure provides a summary ofthe 98th percentile predictions for the three years modeled for CFAC at all federal Class I areas in the vicinity ofthe plant. More detailed modeling results, including the electronic CALPUFF/CALMET files, are available on the WRAP website at http://pah.cert.ucr.edu/aqrn/308/bart.shtml. Because CFAC is subject to BART, EPA Region 8 is requesting that CFAC conduct a BART engineering analysis onthe emission units specified onthe enclosed spreadsheet and submitthe analysis to ouroffice. One ofthe requirements ofthe RHR is that each regional haze implementationplan contain enforceable emission limits for eligible stationary sources based on BART. The BARTanalysis will be used to identify the best system ofcontinuous emissions reduction and corresponding emission limits for each visibility impairing pollutant that is emitted by the CFAC facility. The Clean Air Act and the RHR require that BARTbe established on a case-by-case basis taking into account the available retrofit control options, the costs of compliance, the energy and non-air quality impacts ofcompliance, any pollution control equipment in use at the source, the remaining useful life ofthe source, and the degree of improvement in visibility which may reasonably be anticipated to result from the use ofthe technology. Forpurposes ofthe Regional Haze FIP for Montana, EPA Region 8 is intending to follow its BART Guidelines from 40 CFRPart 51, Appendix Y. The BARTGuidelines are a statement ofEPA's thinking on howbest to meetthe requirements ofBARTinthe CAA and RHR. Thus, in conducting the CFAC BART engineering analysis, you will need to follow the five­3 step BART analysis process identified in Appendix Y, section IV.D, in orderto identify an appropriate BART emission limit. The five steps are:

• Identify all available retrofit control technologies • Eliminate technically-infeasible options • Evaluate the control effectiveness ofremaining control technologies • Evaluate impacts and document the results • Evaluate visibility impacts Foreach ofthese five steps, the BART Guidelines provide detailed guidance for producing an acceptable BART analysis. In addition, your BART analysis should follow other EPA guidance and policies related to BART. Based on the above analysis, you will then identify what you believe is BART for your facility. You will need to provide ajustification for adopting the technology and the emission limits that you select as the best level ofcontrol, including an explanation ofhow the BART factors (costs ofcompliance, energy impacts, non-air quality environmental impacts, remaining useful life ofthe facility, and visibility improvements) were considered (orweighted) in selecting one technically feasible control option overthe others. Your BART analysis should include proposed emission limits for each BART-eligible unit at your facility and for each pollutant subject to BART. For CFAC we have identified sulfur dioxide, nitrogen oxides, and particulate matter as the pollutants that need to be analyzed. Once you submit the BARTanalysis and related documentationto EPA Region 8, we will review the BART analysis and will notify you ofourpreliminary BART determination. We will provide an opportunity for you to respond to ourpreliminary BART determination before making a tinal determination. Ourfinal determination will be included as part ofourRegional Haze FIP for Montana, which will be adopted through notice and commentrulemaking. In orderto meet regulatory schedules and coordinate with other states, EPA Region 8 is requesting that you submit your BART analysis to ouroffices within 90 days from the date of this letter. We understand this is a complicated endeavor, and we are available to answer any questions that you may have onthe RHR, the BART Guidelines, orthe BARTanalysis. We will assist you in any way we can and look forward to working with you. Ifyou choose not to perform or are unable to perform an engineering analysis for CFAC, EPA will perform the BART engineering analysis. Ifyou will not be performing and submitting the BART analysis, we ask that you contact us within 30 days from the date ofthis letter so that we may begin the process ofdeveloping the analysis.4 CFAC may assert a business confidentiality claim covering part or all ofthe information requested by this letter, in the manner described at40 CFR2.203(b). Ifno such claim accompanies the information when it is received by EPA, EPA may make the information available to the public without further notice to CFAC. Information subject to a business confidentiality claim will be disclosed by EPA only to the extent, and by means ofthe procedures, set forth at 40 CFRPart 2, Subpart B. Once again, we look forward to working with you. Ifyouhave any questions regarding the modeling results, please contact Kevin Golden ofmy staffat (303) 312-6442. For questions related to development ofthe BART analysis, please contact Laurel Dygowski at (303) 312­ 6144. Sincerely,

# lOAclL~~~ Stephen S. Tuber .; Assistant Regional Administrator Office ofPartnerships and Regulatory Assistance Enclosure



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## =Columbia Falls AI: SOx

## =816 TPY; NOx

## =11 TPY Class I Area Minimum Distance Max Delta-dv 99 Ul Delta-dv 98'" Delta-dv # Days 98th Percentile by Year 98th 3-Year (km) (dv) (dv) (dv) > 0.5 dv 2001 2002 2003 Average glac Glacier NP 10-50 5.72 4.40 3.79 434 3.13 4.54 3.40 3.69 qlac Glacier NP > 50 0.13 0.03 0.00 0 0.00 0.00 0.02 0.01 boma Bob Marshall 76 0.21 0.13 0.11 0 0.10 0.11 0.09 0.10 mimo Mission Mountains WA 80 0.21 0.10 0.07 0 0.06 0.08 0.06 0.07 camo Cabinet Mountains WA 111 0.24 0.15 0.11 0 0.11 0.12 0.10 0.11 scap Scapegoat 130 0.11 0.07 0.05 0 0.04 0.05 0.05 0.05 selw Selway-BitterrootWilderness 191 0.12 0.04 0.03 0 0.02 0.03 0.03 0.03 gamo Gates ofthe Mountains WA 237 0.07 0.04 0.03 0 0.03 0.03 0.03 0.03 anac Anaconda

- Pintler 263 0.08 0.02 0.02 0 0.01 0.02 0.02 0.02